update our build system to support the experimental L-Release NDK

platform_tools/android/bin/utils/setup_toolchain.sh

 #!/bin/bash
 #
 # setup_toolchain.sh: Sets toolchain environment variables used by other scripts.
 
 # Fail-fast if anything in the script fails.
 set -e
 
 # check that the preconditions for this script are met
 if [ $(type -t verbose) != 'function' ]; then
   echo "ERROR: The verbose function is expected to be defined"
   return 1
 fi
 
 if [ $(type -t exportVar) != 'function' ]; then
   echo "ERROR: The exportVar function is expected to be defined"
   return 1
 fi
 
 if [ $(type -t absPath) != 'function' ]; then
   echo "ERROR: The absPath function is expected to be defined"
   return 1
 fi
 
 if [ -z "$SCRIPT_DIR" ]; then
   echo "ERROR: The SCRIPT_DIR variable is expected to be defined"
   return 1
 fi
 
 function default_toolchain() {
-  API_LEVEL=14
-  NDK_REV=${NDK_REV-8e}
+  NDK_REV=${NDK_REV-10exp}
   ANDROID_ARCH=${ANDROID_ARCH-arm}
+  
+  if [[ $ANDROID_ARCH == *64* ]]; then
+    API_LEVEL=L # Experimental Android L-Release system images
+  else
+    API_LEVEL=14 # Official Android 4.0 system images  
+  fi
 
   TOOLCHAIN_DIR=${SCRIPT_DIR}/../toolchains
   if [ $(uname) == "Darwin" ]; then
     verbose "Using Mac toolchain."
     TOOLCHAIN_TYPE=ndk-r$NDK_REV-$ANDROID_ARCH-mac_v$API_LEVEL
   else
     verbose "Using Linux toolchain."
     TOOLCHAIN_TYPE=ndk-r$NDK_REV-$ANDROID_ARCH-linux_v$API_LEVEL
   fi
   exportVar ANDROID_TOOLCHAIN "${TOOLCHAIN_DIR}/${TOOLCHAIN_TYPE}/bin"
@@ skipping 44 matching lines @@
 exportVar RANLIB "$ANDROID_TOOLCHAIN_PREFIX-ranlib"
 exportVar OBJCOPY "$ANDROID_TOOLCHAIN_PREFIX-objcopy"
 exportVar STRIP "$ANDROID_TOOLCHAIN_PREFIX-strip"
 
 # Create symlinks for nm & readelf and add them to the path so that the ninja
 # build uses them instead of attempting to use the one on the system.
 # This is required to build using ninja on a Mac.
 ln -sf $ANDROID_TOOLCHAIN_PREFIX-nm $ANDROID_TOOLCHAIN/nm
 ln -sf $ANDROID_TOOLCHAIN_PREFIX-readelf $ANDROID_TOOLCHAIN/readelf
 exportVar PATH $ANDROID_TOOLCHAIN:$PATH